Reinforced-fin rotating band



Oct. 15, 1957 c w. MUSSER REINFORCED-FIN ROTATING BAND Filed Jan. 15, 1954 VEN TOR. MUSSER IN 0 WALTON BY mmwawm ma i nmmn'roamsvs:

United States Patent 9 l REINFORCED-FIN ROTATING BAND C Walton Musser, Philadelphia, Pa., assignor to theUnited States of America as represented by the Secretary of the Army Application January 15, 1954, Serial No. 404,402 1 Claim. (Cl. 10293) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the paymentof any royalty thereon.

This invention relates to projectiles and more particularly to plastic reinforced, fin-type, rotating bands for rotary or spin stabilized projectiles.

For reasons familiar to those skilled in the ordnance art, it is customary to provide the rear portion of rotary projectiles with what is known as a rotating band in order to elfect rotation or spin of the projectile during flight. The rotating band, which is conventionally of softer material than the gun metal, is somewhat larger in diameter than the groove diameter, and is thus larger than the land diameter, of a rifled gun barrel. Consequently, the band, upon beingforced through the bore by the firing of the projectile, is engraved by the rifling in the barrel. This engraving puts splineson the rotating band. which positively engage and are rotated by the rifling and which in turn impart rotation to the projectile. The close fit of the engraved band with the interior surface of the gun barrel also produces a gas-tight seal which effectively prevents escape of those gases which are required to propel the projectile out of the barrel.

As a result of the engraving, very great stresses are imparted to the projectile wall and to the rifle barrel; the engraving forces tending to expand the barrel and compress the body of the projectile. Accordingly, that part of the projectile wall thickness, which is provided to withstand the engraving force, wastefully reduces the payload of the projectile; and, also, the gun barrel of the gun wall thickness provided to withstand the engraving force noticeably increases the weight of the gun. Furthermore, the energy consumed in engraving the band reduces the total energy available for propelling the projectile, thereby reducing its range. As a result, there has been a considerable amount of experimentation to develop a rotating band whichwould not require an engraving force of the magnitude presently required of the conventionaL'metal bands.

Some experiments have been made with plastic rotating bands of a more or less conventional shape. While such bands, of various plastic compositions, do obtain a l-eduction in the engraving force required, difliculty has been encountered with, overcoming the tendency of the bands to be thrown loose, of .the. projectile upon exiting .the muzzle of the gun. Detachment of the band in this manner not only impairs the flight of the projectile but creates hazards which might include the loss of life and property. Furthermore, such type of plastic band is usually insufiiciently strong enough to transmit the rotational velocity necessary to give stability to the projectile. Always present with the use of plastics is the serious problem of expansion due to the variation in temperatures. For example, a plastic band which is sufiiciently large for the intended purpose at 20 F. might very well expand and become too large at 120 F. While the projectile will fire at the higher temperature, increased stresses are placed upon the projectile and the gun barrel, negativing the advantages expected from the use of the plastic band.

Although these and other known endeavors have represented considerable advances in the art, a still further improved rotating band long has been sought.

It is, therefore, an object of this invention to provide an improved rotating band for rotary type projectiles which will overcome the above, as well as other disadvantages of the prior art.

Accordingly, it is another object of this invention to provide for projectiles a rotating band which has suflicient strength to impart the desired rotation to the projectile, while requiring a reduced force for engraving purposes.

. A further object of this invention is to provide forv projectiles a rotating band which will reduce the wearing elfect on the rifling of the gun caused by the engraving of the rotating band.

An additional object of this invention is to reduce the weight of projectiles of the rotary type by permitting a reduction of the projectile wall thickness, thereby increasing the payload of such projectiles.

A still further object of this invention is to provide a rotating band utilizing a reduced engraving force thereby to enhance the exterior ballistics of the projectile, reduce wear on the barrel of the gun and which will effect a savings in the weight of the projectile.

In furtherance of these objects I have provided a rotating band for rotary type projectiles which incorporates the favorable features of metallic and plastic materials. This rotating band comprises a plurality of spaced metallic fins which are integral with the projectile. The space between each of the relatively thin fins is filled with a plastic material, which material is also banked-up outside, the first and last fins. In this type of rotating band, the plastic is used principally as a means of supporting or reinforcing the fins which transmit the rotational force to the projectile. The plastic reinforcement thus prevents damage to the fins prior to insertion of the projectile into the gun and prevents the engraving forces from completely bending back each of the fins upon firing the projectile. As such, the fins bend back only at the places where the lands of the rifling contact them, while being supported and held up at the places in the grooves between adjacent lands.

By utilizing the plastic material in this manner, the engraving forces are reduced while the force-transmitting strength of the band is retained by the metallic fins. Furthermore, since the plastic used in this particular type of band is very thin when compared with the conventional rotating band, the expansion problems heretofore experienced with the use of plastics are substantially eliminated.

All of the foregoing as Well as other objects and advantages of this invention will become apparent from a study of the following specification, taken in conjunction with the accompanying drawings, wherein like characters of reference, indicate corresponding parts throughout the several views and wherein: r

Figure 1 is a front elevational view, broken away in parts, of av complete roundof ammunitiomishowing a rotating band in accordance with. this invention .in association with the projectile portion thereof, and

Figure 2 is a sectional view taken along line'Z-2 of Figure l, enlarged to show the rotating band in detail.

Referring now to the drawings, and more particularly to Figure 1, a rotating band, generally designated by the reference numeral 1, of thetype advocated by this invention is shown in encircling association with the rear portion of a rotary type projectile, which is generally designated by the reference numeral 3. For the purposes of illustration, the projectile is shown to project from the open end of a metallic shell case 5, although it is to be Patented- Oct. 15, 1957 understood that this invention is not so limited but may be applied to all types of rotary projectiles which are engraved by a gun barrel (not shown) upon being fired, including recoilless-rifie type projectiles. Within the shell case 5 is the charge of propellant powder 7 which, upon being exploded by a detonating charge (not shown) at the time of firing, propels the projectile through the rifled bore of the gun.

The projectile 3, which may be any of the several rotary types, relies upon the rotating band 1 to impart the rotary movement, derived from the engagement of the band with the riiling of the gun, to the projectile. Referring to Figure 2 of the drawings, the rotating band 1 is shown to comprise a plurality of spaced, relatively thin, concentric annular fins 9 arranged on the rear portion of the projectile. Fig. 2 of the drawing discloses what is meant by the fins being relatively thin as mentioned in the previous sentence, inasmuch as the fins are there shown to be substantially greater in radial length than their axial thickness. These fins 9 are integral with and extend from a short distance beneath to a short distance above the surface 11 of the projectile. A preferred method of fabricating these fins is carried out by providing a homogeneous band on the projectile in the desired location and then forming the fins by removing the metal therebetwcen on a machine such as a lathe or by forming them by a rolling process. in other words, a method of fabricating the fins is carried out by providing the band, just referred to, and then forming a plurality of circumferential grooves side by side in the projectile at that place; the annular walls between the grooves constituting the desired fins.

From Fig. 2, it is evident that the groove between each of the radial fins 9 and between each end fin and the adjacent shoulders 13, 15, formed on the projectile, is of appreciably greater width (i. e., dimension in a direction aiong the projectile axis) than the thickness of each of the fins and is occupied by a filler type material 17 such as ethyl cellulose, for example, which is readily engraved when the projectile is fired through a rifled gun barrel; the filler material being bankedup against the outside of each end fin, is best shown in Fig. 2. These annular fins 9, together with the plastic filler material 17, present a smooth surfaced, composite band, concentric with and of greater diameter than the projectiles rear bourrelet surface 11. The plastic filler material can be molded directly to the projectile, in a conventional manner, thereby assuring an intimate association with the projectile metallic surfaces.

In accordance with accepted ordnance practice, this composite band is also made somewhat larger in diameter than the diameter across the riding of the gun barrel in which the projectile equipped with such band is to be fired. Consequently, when such projectile is fired, the riding will engrave the rotating band; the engraved portions of the fins being displaced toward the rear of the projectile over the filler material and into the respective grooves in the projectile, which grooves receive and accommodate the fin engraved portions. Following the path of the rifiing, the rotating band imparts the desired rotary motion to the projectile during the course of its forward travel.

For purposes of clarification, the terms plastic, plastic material, and the like, as herein referred to, are used to designate a substance which belongs to that group of materials commonly known as plastics, rather than to define a particular state of being pliable. It will also be appreciated that other materials having the desirable characteristics may be substituted for the referred-to plastics, as a matter of choice, if desired.

It will become apparent to those skilled in the art that other and different arrangements may be used within the purview of this invention. For example, the outwardly extending metallic fins could be arranged in the form of a continuous spiral, encircling the projectile rather than in the discrete annular form disclosed. It is, therefore, to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same and that changes in the shape, size and arrangement of the parts may be resorted to without departing from the spirit of the invention. Accordingly, it is desired that the form disclosed be taken as illustrative and not as limiting. Furthermore, I do not wish to be limited beyond the limitations which may be imposed by the following claim.

I claim:

In a hollow projectile having a tapered forward end portion, a rotating band on the rear surface, and a cylindrical surface axially between said rotating band and tapered end portion, the combination therewith of the improvement enabling a wall thickness of the projectile radially within the rotating band to be of minimum thickness whereby a greater space is made available within the projectile for whatever load may be carried thereby and whereby minimum engraving force is needed within said rotating band by the lands and grooves of a gun in which the projectile is to be fired, said improvement including flexible, radial fins in said rotating band integrally anchored to a body portion of said projectile radially within a projection of each cylindrical surface within said fins, said fins being spaced apart by peripheral grooves between them, the fins and grooves occupying the entire axial length of said rotating band, the radial length of said fins being enough for about half their radial length to project beyond said projection of said forward cylindrical surface in order that engraving of said fins by rifling in a gun may occur in the outer portions of the fins, said fins having a flexibility resulting from their radial length being substantially greater than their axial thickness, the axial spacing of said fins by said grooves being sufficient to allow fiexure of said fins during engraving and avoid contact between adjacent fins, and a yieldable supporting plastic filler between said fins, within said grooves, capable of being deformed by flexure of said fins during engraving while simultaneously supporting the fins during engraving flexure, said filler extending radially to a periphery of said fins and having a deformability within a range of that for ethyl cellulose.

References Cited in the file of this patent FOREIGN PATENTS 809,845 France Mar. 10, 1937 526,941 Great Britain Sept. 30, 1940 698,998 Germany Nov. 21, 1940 118,598 Australia June 8, 1944 962,105 France Dec. 5, 1949 

